In prior art systems for measuring phase relationship between two noisy signals, it is well established that there are three basic problems: (1) The presence of noise introduces errors in the measurement, (2) analog techniques are relatively slow in producing useful measurements, usually requiring the measurement to be made over many periods of the signals being measured and (3) prior art systems are frequently not capable of measuring phase differences over the full range of from .degree. to 360.degree..
Serious attempts to solve some of these problems have compounded others of them. Digital design approaches to these problems have been used but they have not solved all three problems listed above and they have tended toward high parts count, expense and volume in the circuits utilized.